Japan's weather agency says a strong earthquake with a preliminary magnitude of 6.1 struck off the northern Japanese coast.

The Meteorological Agency says there was no danger of a tsunami, or seismic waves, from the 8:30 p.m. (1130 GMT) quake, which occurred about 20 miles (30 kilometers) below the ocean's surface off the coast of Fukushima.

There were no immediate reports of damage or injuries.

Japan is one of the world's most earthquake-prone countries.